Stainless steel has good strength and good
corrosion resistance ability in higher temperature environments. The most
searched SS grade is 304 and 316, due to the prominent features it offers to
the applications. These grades are extensively used in many application ranges
from moderate temperatures to high temperatures such as superheaters, heat
exchangers, valves and other heating applications. However, their heat
capacities differ from each other that vary its properties.
Temperature
range of 304 grades:
SS 304 grade is from the 300 series of
austenitic stainless steel modified with controlled carbon chemistry for
increased strength up to 1500 deg F. UNS S30400 is a unified numbering system
of 304 grades. Generally, it is the modified version of 18/8 chromium and
nickel base austenitic alloy. The carbon content present on it about 0.04 % to
10 % that increases its strength above 800 deg F. It is the most cost-effective
and versatile alloy suitable for a wide range of applications.
Stainless
Steel 304 Tubes has good resistance to atmospheric corrosion and many
organic and inorganic compounds in moderately oxidizing to severe reducing conditions.
It has the highest chromium content that provides resistance to oxidizing
agents such as nitric acids up to 176 deg F temperature.
This grade also opposes harsh organic acids
like acetic acids. In addition to the nickel, it offers resistance to moderate
reducing solutions like phosphoric acids even in the higher concentration too.
This grade can offer service in caustic solutions free of chlorides at nominal
temperatures.
The hot working temperature of this grade
is between 1652 deg F to 2102 deg F, the same temperature is recommended for the hot working process. In order to acquire maximum corrosion resistance, this
grade is subject to the annealing process and quenched with water.
A higher concentration of chlorides, it is
susceptible to pitting and crevice corrosion. The high molybdenum content is
needed for the successful performance in the most severe conditions.
Temperature
range of 316 grades:
Alloy 316 (UNS S31600) /S31603) is
chromium, nickel, and molybdenum austenitic stainless steel. It is designed for
improved corrosion resistance in the high temperatures. These are often
utilized in the process streams that contain halides and chlorides. In addition
to molybdenum, its resistance ability to corrosion and pitting is enhanced. 316
grades provide excellent properties such as stress to rupture strength and
tensile strength even in the hoisted temperatures. This grade is weldable with more
standard techniques.
These are not corroded in process streams.
SS 316 performs well in sulfur-containing environments such as that encountered
in industries. This alloy can be utilized in higher concentrations at
temperatures up to 120 deg F.
The working temperatures of this alloy are ranging
from 1700 deg F to 2200 deg F. These are also subject to the hot working
process at the same temperatures. The annealing process is performed at 1900
deg F to acquire higher corrosion resistance. These are also quenched with
water.
So, these are the temperature ranges of
stainless steel 304 and 316. Choose one as per your application suitability.
